Effect And Regulation Mechanism Of Zero Valent Iron-Anaerobic Biological Method In Dyeing Wastewater Treatment

At the base of understanding the actuality of dye wastewater treatment, the present experiment proposed the coupling technique between anaerobic treatment and micro-electrolysis to solve the problem of dye wastewater, i.e. large quantity, high alkaline, high salinity, high color and high content of refractory material, and investigated the processing parameters and influencing factors through the treatment of actual wastewater and simulated wastewater. By comparing the effect of single anaerobic treatment (SAT), single micro-electrolysis treatment and anaerobic treatment coupled micro-electrolysis (ATCM) on treating actual dye wastewater, the experiment found the characteristics and the problem of ATCM, then treated simulated wastewater by the coupling technique to study its operation mechanism and electrochemical improvement (called improved ATCM), and studied the reduction of activate hydrogen to dye through electrochemical method.In actual dye wastewater treatment, single anaerobic treatment) needed more time to achieve the maximum efficiency. The COD remival was 45%, and the effluent was alkaline and dark gray; But the impact of HRT on single micro-electrolysis was weak, and the COD removal was about 50%; The efficiency of ATCM was higher than that of SAT. The color of effluent was low, light blue, and turning to dark gray gradually. The COD removal of iron bed was 40% of the total COD removal, but became 5% in the late operation, and the water turned to gray black gradually.According to the problems in tratment of actual wastewater, the experiment made deep investigation in treating simulated dye wastewater to study the effect and impact of external electric field on the coupling technique. The color and COD removal reached 90% and 73% for improved ATCM and iron bed played a more important role in color removal. The decolorization efficiency dropped as the Na2SO4 concentration increased, and it achieved the maximum value at pH 9. The adsorption of dye and its degradation in anaerobic sludge of SAT was less, and the microorganism did not have stable form, but after introducing iron and external electric field, anaerobic sludge began to adsorb dye and microorganism was spirillum. Through analysis of FTIR and SEM, only the auxochrome group and bridging group were removed in anaerobic sludge bed, but all group were removed in iron bed, and the solubilization of organic solid covering the iron surface was improced when adding external electric field. Without external electric field, the covering on iron surface was close and compact, while adding external electric field, it became loose, and the granule became larger and had the characteristic of reticular formation.The experiment studied the fuction of activate hydrogen in coupling technique by electrochemical method to understand the mechanism of the coupling technique. The reactive dye could adsorbed on electrode as weak acid. The protonation of dye molecule could accelerate the production of atomic hydrogen. The decolorization efficiency using potentiostatic polarization at -0.18V was highest than that at other polarization potential because the proportion between adsorbed dye and adsorbed atomic hydrogen on electode was optimum. The decolorization efficiency declined following the increase of initial dye concentration.